Metals and oxidative stress in aquatic decapod crustaceans: A review with special reference to shrimp and crabs.

The objective of this review is to synthetize knowledge of the relationship between metals and oxidative stress in aquatic crustaceans (mainly shrimp and crabs) to analyze antioxidant responses when organisms are exposed to metals because the direct metal binding to the active site of enzymes inactivates most of the antioxidant systems. This study reviewed over 150 works, which evidenced that: (i) antioxidant defense strategies used by aquatic decapod crustaceans vary among species; (ii) antioxidant enzymes could be induced or inhibited by metals depending on species, concentration, and exposure time; and (iii) some antioxidant enzymes, as superoxide dismutase increase their activity in low metal levels and time exposures, but their activities are inhibited with higher metal concentrations and exposure time.

DNA Damage and Immunological Responses in the Whiteleg Shrimp (Litopenaeus vannamei) Exposed to Sublethal Levels of Mercury.

Litopenaeus vannamei juveniles were exposed to sublethal levels (2.33-18.03 µg/L) of inorganic mercury. Time of exposure (0, 24 and 168 h) was a source of DNA damage. Mean comet tail length not changed significantly with mercury concentrations and exposure time, and this parameter cannot be used to assess DNA damage in this shrimp. Total hemocyte count showed a trend to decrease according to the increase of mercury concentrations, although no significant difference between treatments with mercury was observed. The phenoloxidase (PO) activity was not influenced by the time of exposure. At the end of the experiment, the PO in organisms exposed to 18.03 µg/L was different from the control. The time of exposure has a more important influence in superoxide dismutase than the concentration of mercury. According to these results, a suitable criterion of water quality for long-term exposure of L. vannamei should be lower than 2 µg/L of mercury.